The present invention relates generally to integrated circuit designs, and more particularly to high voltage input/output (I/O) drivers without using thick-oxide devices.
Semiconductor technology is evolving into the very deep sub-micron geometries of less than 100 nanometers (nm) to integrate more complex functionality at higher performance on a single chip. Sub-100 nm devices offer more complex functionality and higher performance, but not without a cost.
It has been observed that when a transistor channel length is small enough, current continues to flow even during standby states because of leakage. Therefore, the supply voltage must be scaled down accordingly to minimize such leakage. However, the I/O voltage for conventional I/O drivers still remains at a high voltage level, such as 3.3V or 2.5V, for compatibility with existing parts. Conventionally, thick-oxide devices are usually used for I/O drivers and thin-oxide devices are used for other circuits operating with the down-scaled supply voltage. The conventional I/O drivers using thick-oxide devices require additional masks during fabrication process, thereby making the process costly and time consuming. For example, it is typical that in order to include thick-oxide devices in semiconductor processing, four or five additional masks must be added to produce those devices. While there have been attempts to solve this issue, those attempts are either too complicated or limited for practical uses.
Desirable in the art of integrated circuit designs are designs that eliminate the need of using thick-oxide devices in high voltage I/O drivers.